Digital BW, The Print

Austin writes:

> I don't believe you know what you're talking about.

Read my example in my post to Peter with respect to yellow-sensitive film,
and tell me how you'd duplicate the response of this film in a conversion
from RGB.

If RGB were sufficient for transformations from any curve to any other
curve, then it would be impossible for us to see yellow by mixing red and
green.  Since, however, we _do_ see yellow by mixing red and green, clearly
there is information lost in the conversion to RGB.  Once a yellow surface
is photographed in RGB, we can never know if it was really yellow, or just a
blend or red and green.  This proves that the conversion involves an
irreversible loss of information, and so it is impossible to reconstruct the
curve of any other film or sensor from RGB alone.